Papers by Keyword: Self-Consistent

Abstract: The present work deals with the analytical resolution of the problem of viscoelastic coated inclusion embedded in a viscoelastic matrix.In a first step, we will study the problem of a linear viscoelastic inclusion, without coating, embedded in a linear viscoelastic matrix.Then, the problem of coated viscoelastic inclusion considering the coating as a thin layer whose viscoelastic properties are different from those of the inclusion and the matrix is performed.The resolution of this problem will be based simultaneously on the Green function technique as well as the interface operator. The analytical expression of the solution is obtained by assuming the isotropy of the matrix as well as the spherical shape of the coatedinclusion.These results are used to determine the effective properties of a heterogeneous medium from a self-consistent approach taking into accountthe interactions between coated inclusions and the equivalent homogeneous medium.

Abstract: In this paper, the effective properties of magnetoelectroelastic heterogeneous materials with ellipsoidal multi-inclusions are modeled and numerically investigated. The modeling is based on the integral equation that takes into account the multi-coated effect as well as the magnetoelectroelastic interfacial operators and global and local concentration tensors. Various types and kinds of coatings can be considered. The effective properties are predicted based on various micromechanical models such as Mori-Tanaka, Self-Consistent and Incremental Self-Consistent. These properties are presented in terms of the volume fractions of the multi-coated inclusions, thicknesses of the coatings, type and kind of inclusions.

Abstract: A theoretical model based on self-consistent approximation is proposed to explore the effect of grain size distribution on the local mechanical response of nanocrystalline (nc) materials. The representative volume element (RVE) is composed of grains randomly distributed with a grain size distribution following a log-normal statistical function. The grain interior and grain boundary are taken as an integral object to sustain deformation mechanisms of grain-boundary sliding, grain-boundary diffusion and grain-interior plasticity. Local plastic strains and internal stresses, developing within the RVE, have been recorded and discussed.

Abstract: This work presents a micromechanics-based model to investigate the effective thermo-electric properties of piezoelectric composite materials. The effective thermo-electric properties are derived by considering a multi-coated ellipsoidal inhomogeneity embedded in a host material in the framework of the generalized self-consistent method (GSCM). An incremental scheme, in which the reinforcements are incrementally put in the host material, is implemented. The validation of the micromechanical model is performed with experimental data. The model proposed has a wide range of applications and can be extended to other physical properties.

Abstract: The high-temperature deformation behavior of the single-phase α (Ti-7.0Al-1.5V) and α + β (Ti-6Al-4V) alloy were determined and compared within the framework of self-consistent scheme at various temperature ranges. For this purpose, isothermal hot compression tests were conducted at temperatures between 650°C ~ 950°C to determine the effect of α/β phase volume fraction on average flow stress under hot-working condition. The flow behavior of α phase was estimated from the compression test results of single-phase α alloy whose chemical composition is close to that of α phase of Ti-6Al-4V alloy. On the other hand, the flow stress of β phase in Ti-6Al-4V was predicted by using self-consistent method. The flow stress of α phase was higher than that of β phase above 750°C, while the β phase revealed higher flow stress than α phase at 650°C. Also, at temperature above 750°C, the predicted strain rate of β phase was higher than that of α phase. It was found that the relative strength between α and β phase significantly varied with temperature.

Abstract: In this contribution we present how to implement the calculation of average field fluctuations inside the grains of a thermoelastic aggregate in terms of the derivatives of the stress potential given by the standard linear self-consistent (SC) model, and how this statistical information can be used to generate second-order estimates for the mechanical behavior of nonlinear viscoplastic polycrystals, by means of a rigorous non-linear homogenization procedure. To illustrate the differences between this second-order (SO) self-consistent approach and the classical first-order SC approximations, we compare them in terms of their predictions of the effective behavior of random fcc polycrystals as a function of their rate-sensitivity, and of the texture evolution in hcp ice polycrystals under uniaxial compression. In the latter case, the SO approximation is the only one able to predict a substantial accommodation of deformation by basal slip, even when the basal poles become strongly aligned with the compression direction and the basal slip systems became unfavorably oriented.

Abstract: In this paper a procedure for the global optimization of mid-infrared GaAs/AlGaAs quantum cascade lasers that relies on the method of simulated annealing is presented. We propose a double longitudinal optical phonon resonance design obtained via a ladder of three states, with subsequent pairs separated by optical phonon energy. Addition of an extra level decreases the lower laser level population by enabling an efficient extraction into the injector region. The output characteristics of the optimized structures are calculated using the full self–consistent rate equation model, which includes all of the relevant scattering mechanisms. We also presented the experimentally measured output characteristics of an initial device, which are in agreement with the numerically calculated values, confirming the good design capabilities of the applied procedure.